contrib: add sipa's github-merge script

3 files changed, 215 insertions, 0 deletions

diff --git a/contrib/README.md b/contrib/README.md
index d1cdd7eb38..167b5df4e1 100644
--- a/contrib/README.md
+++ b/contrib/README.md
@@ -52,3 +52,7 @@ tests each pull and when master is tested using jenkins.
 ### [Verify SF Binaries](/contrib/verifysfbinaries) ###
 This script attempts to download and verify the signature file SHA256SUMS.asc from SourceForge.
 
+### [Developer tools](/control/devtools) ###
+Specific tools for developers working on this repository.
+Contains the script `github-merge.sh` for merging github pull requests securely and signing them using GPG.
+
diff --git a/contrib/devtools/README.md b/contrib/devtools/README.md
new file mode 100644
index 0000000000..55d5d24cca
--- /dev/null
+++ b/contrib/devtools/README.md
@@ -0,0 +1,38 @@
+Contents
+===========
+This directory contains tools for developers working on this repository.
+
+github-merge.sh
+----------------
+
+A small script to automate merging pull-requests securely and sign them with GPG.
+
+For example:
+
+  ./github-merge.sh bitcoin/bitcoin 3077
+
+(in any git repository) will help you merge pull request #3077 for the
+bitcoin/bitcoin repository.
+
+What it does:
+* Fetch master and the pull request.
+* Locally construct a merge commit.
+* Show the diff that merge results in.
+* Ask you to verify the resulting source tree (so you can do a make
+check or whatever).
+* Ask you whether to GPG sign the merge commit.
+* Ask you whether to push the result upstream.
+
+This means that there are no potential race conditions (where a
+pullreq gets updated while you're reviewing it, but before you click
+merge), and when using GPG signatures, that even a compromised github
+couldn't mess with the sources.
+
+Setup
+---------
+Configuring the github-merge tool for the bitcoin repository is done in the following way:
+
+    git config githubmerge.repository bitcoin/bitcoin
+    git config githubmerge.testcmd "make -j4 check" (adapt to whatever you want to use for testing)
+    git config --global user.signingkey mykeyid (if you want to GPG sign)
+
diff --git a/contrib/devtools/github-merge.sh b/contrib/devtools/github-merge.sh
new file mode 100755
index 0000000000..e42b71a54a
--- /dev/null
+++ b/contrib/devtools/github-merge.sh
@@ -0,0 +1,173 @@
+#!/bin/bash
+
+# This script will locally construct a merge commit for a pull request on a
+# github repository, inspect it, sign it and optionally push it.
+
+# The following temporary branches are created/overwritten and deleted:
+# * pull/$PULL/base (the current master we're merging onto)
+# * pull/$PULL/head (the current state of the remote pull request)
+# * pull/$PULL/merge (github's merge)
+# * pull/$PULL/local-merge (our merge)
+
+# In case of a clean merge that is accepted by the user, the local branch with
+# name $BRANCH is overwritten with the merged result, and optionally pushed.
+
+REPO="$(git config --get githubmerge.repository)"
+if [[ "d$REPO" == "d" ]]; then
+  echo "ERROR: No repository configured. Use this command to set:" >&2
+  echo "git config githubmerge.repository <owner>/<repo>" >&2
+  echo "In addition, you can set the following variables:" >&2
+  echo "- githubmerge.host (default git@github.com)" >&2
+  echo "- githubmerge.branch (default master)" >&2
+  echo "- githubmerge.testcmd (default none)" >&2
+  exit 1
+fi
+
+HOST="$(git config --get githubmerge.host)"
+if [[ "d$HOST" == "d" ]]; then
+  HOST="git@github.com"
+fi
+
+BRANCH="$(git config --get githubmerge.branch)"
+if [[ "d$BRANCH" == "d" ]]; then
+  BRANCH="master"
+fi
+
+TESTCMD="$(git config --get githubmerge.testcmd)"
+
+PULL="$1"
+
+if [[ "d$PULL" == "d" ]]; then
+  echo "Usage: $0 pullnumber [branch]" >&2
+  exit 2
+fi
+
+if [[ "d$2" != "d" ]]; then
+  BRANCH="$2"
+fi
+
+# Initialize source branches.
+git checkout -q "$BRANCH"
+if git fetch -q "$HOST":"$REPO" "+refs/pull/$PULL/*:refs/heads/pull/$PULL/*"; then
+  if ! git log -1q "refs/heads/pull/$PULL/head" >/dev/null 2>&1; then
+    echo "ERROR: Cannot find head of pull request #$PULL on $HOST:$REPO." >&2
+    exit 3
+  fi
+  if ! git log -1q "refs/heads/pull/$PULL/merge" >/dev/null 2>&1; then
+    echo "ERROR: Cannot find merge of pull request #$PULL on $HOST:$REPO." >&2
+    exit 3
+  fi
+else
+  echo "ERROR: Cannot find pull request #$PULL on $HOST:$REPO." >&2
+  exit 3
+fi
+if git fetch -q "$HOST":"$REPO" +refs/heads/"$BRANCH":refs/heads/pull/"$PULL"/base; then
+  true
+else
+  echo "ERROR: Cannot find branch $BRANCH on $HOST:$REPO." >&2
+  exit 3
+fi
+git checkout -q pull/"$PULL"/base
+git branch -q -D pull/"$PULL"/local-merge 2>/dev/null
+git checkout -q -b pull/"$PULL"/local-merge
+TMPDIR="$(mktemp -d -t ghmXXXXX)"
+
+function cleanup() {
+  git checkout -q "$BRANCH"
+  git branch -q -D pull/"$PULL"/head 2>/dev/null
+  git branch -q -D pull/"$PULL"/base 2>/dev/null
+  git branch -q -D pull/"$PULL"/merge 2>/dev/null
+  git branch -q -D pull/"$PULL"/local-merge 2>/dev/null
+  rm -rf "$TMPDIR"
+}
+
+# Create unsigned merge commit.
+(
+  echo "Merge pull request #$PULL"
+  echo ""
+  git log --no-merges --topo-order --pretty='format:%h %s (%an)' pull/"$PULL"/base..pull/"$PULL"/head
+)>"$TMPDIR/message"
+if git merge -q --commit --no-edit --no-ff -m "$(<"$TMPDIR/message")" pull/"$PULL"/head; then
+  if [ "d$(git log --pretty='format:%s' -n 1)" != "dMerge pull request #$PULL" ]; then
+    echo "ERROR: Creating merge failed (already merged?)." >&2
+    cleanup
+    exit 4
+  fi
+else
+  echo "ERROR: Cannot be merged cleanly." >&2
+  git merge --abort
+  cleanup
+  exit 4
+fi
+
+# Run test command if configured.
+if [[ "d$TESTCMD" != "d" ]]; then
+  # Go up to the repository's root.
+  while [ ! -d .git ]; do cd ..; done
+  if ! $TESTCMD; then
+    echo "ERROR: Running $TESTCMD failed." >&2
+    cleanup
+    exit 5
+  fi
+  # Show the created merge.
+  git diff pull/"$PULL"/merge..pull/"$PULL"/local-merge >"$TMPDIR"/diff
+  git diff pull/"$PULL"/base..pull/"$PULL"/local-merge
+  if [[ "$(<"$TMPDIR"/diff)" != "" ]]; then
+    echo "WARNING: merge differs from github!" >&2
+    read -p "Type 'ignore' to continue. " -r >&2
+    if [[ "d$REPLY" =~ ^d[iI][gG][nN][oO][rR][eE]$ ]]; then
+      echo "Difference with github ignored." >&2
+    else
+      cleanup
+      exit 6
+    fi
+  fi
+  read -p "Press 'd' to accept the diff. " -n 1 -r >&2
+  echo
+  if [[ "d$REPLY" =~ ^d[dD]$ ]]; then
+    echo "Diff accepted." >&2
+  else
+    echo "ERROR: Diff rejected." >&2
+    cleanup
+    exit 6
+  fi
+else
+  # Verify the result.
+  echo "Dropping you on a shell so you can try building/testing the merged source." >&2
+  echo "Run 'git diff HEAD~' to show the changes being merged." >&2
+  echo "Type 'exit' when done." >&2
+  bash -i
+  read -p "Press 'm' to accept the merge. " -n 1 -r >&2
+  echo
+  if [[ "d$REPLY" =~ ^d[Mm]$ ]]; then
+    echo "Merge accepted." >&2
+  else
+    echo "ERROR: Merge rejected." >&2
+    cleanup
+    exit 7
+  fi
+fi
+
+# Sign the merge commit.
+read -p "Press 's' to sign off on the merge. " -n 1 -r >&2
+echo
+if [[ "d$REPLY" =~ ^d[Ss]$ ]]; then
+  if [[ "$(git config --get user.signingkey)" == "" ]]; then
+    echo "WARNING: No GPG signing key set, not signing. Set one using:" >&2
+    echo "git config --global user.signingkey <key>" >&2
+    git commit -q --signoff --amend --no-edit
+  else
+    git commit -q --gpg-sign --amend --no-edit
+  fi
+fi
+
+# Clean up temporary branches, and put the result in $BRANCH.
+git checkout -q "$BRANCH"
+git reset -q --hard pull/"$PULL"/local-merge
+cleanup
+
+# Push the result.
+read -p "Type 'push' to push the result to $HOST:$REPO, branch $BRANCH. " -r >&2
+if [[ "d$REPLY" =~ ^d[Pp][Uu][Ss][Hh]$ ]]; then
+  git push "$HOST":"$REPO" refs/heads/"$BRANCH"
+fi